Splenic myeloid metaplasia in warm autoimmune hemolytic anemia (wAIHA): a retrospective study

Splenic myeloid metaplasia (SMM) is a kind of extramedullary hematopoiesis, whereas its clinical significance in wAIHA remains unclear. The aim of this study is evaluating the frequency and clinical characteristics of SMM, compared with splenic-congestion (SC). We included patients with wAIHA treated in a Mexican tertiary hospital between January 1992 and December 2015. All patients received steroids as first-line treatment and splenectomy as second-line treatment. Among the thirty-six splenectomized patients, 15 (41.6%) and 21 (58.4%) were diagnosed as SMM and SC, respectively. No differences were found in clinical characteristics between two groups. SMM patients showed lower platelet count (147×10 /L vs. 240×10 /L, =0.02) and higher presence of anti-dsDNA antibodies (40% vs. 4.7%, =0.01) than SC patients. Although the complete response (CR) rate with first-line treatment was lower in SMM patients (13.3% vs. 47.6%; =0.04), post-splenectomy median disease-free-survival (DFS) was longer (16.2 mo vs. 5.1 mo; =0.19). Univariate/multivariate analysis showed that achieving CR during first-line treatment (OR 0.3, 95% CI: 0.03-0.94, =0.03) and higher platelet count (OR 0.99, 95% CI: 0.98-0.99, =0.03) were protective factors for SMM; and anti-dsDNA titer higher than 9.6 IU/dL was a risk factor for SMM (OR 2.76, 95% CI: 1.48-5.14,